Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

Ph.D. in Engineering Science


Civil Engineering

First Advisor

Craig J. Hickey

Second Advisor

Yacoub Najjar

Third Advisor

Elizabeth K. Ervin

Relational Format



Geophysical methods provide a rapid, economical, non-invasive, and spatial coverage of the subsurface in terms of geophysical properties. On the other hand, geophysical methods can generate multiple geophysical anomalies. An anomaly on a seismic refraction or an electrical resistivity tomogram is an area that has different values compared to its surrounding. Geophysical anomalies in dams and levees can be due to the overall heterogeneity of the subsurface, structures such as principal spillways, artifacts of inversion software, or to a true compromised location, such as an air void due to internal erosion or seepage. Therefore, there is uncertainty involved with using geophysical methods where an anomaly does not necessarily represent a true compromised zone. Identification of true compromised zones requires an invasive geotechnical investigation, such as drilling. To identify anomalies that are associated with true compromised zones, multiple types of geophysical surveys are commonly conducted. Although the use of multiple geophysical methods and qualitative side-by-side interpretation can reduce this problem to some degree, a more quantitative analysis in identifying the type of compromised zones is required. Such analysis can be achieved with the application of cross-plot analysis. With the use of cross-plot analysis, it is possible to relate and map results from multiple geophysical surveys to more commonly used geotechnical terms such as porosity and moisture content. This research develops the use of cross-plot analysis using time-lapse seismic refraction tomography and electrical resistivity tomography for the assessment of earthen dams and levees. The focus of this research is on the development of a method for quantifying the bounding seismic velocity and electrical resistivity values, which then divide the subsurface integrity conditions into different groups. A new approach of using preliminary and laboratory geophysical measurements to define cross-plot constraints is presented. This work will separately target different types of compromised zones, such as sand zones and dry compacted clay zones, by incorporating their unique seismic and electrical resistivity attributes into the cross-plot analysis. A new approach of cross-plot analysis using external physical constraints derived from geophysical surveys and theoretical models at the Francis Levee Site is also presented.


Emphasis: Civil Engineering



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